Mafia Island usually works best after safari, especially after Southern Tanzania routes. It is quieter and more remote than Zanzibar, so flight logistics and enough beach nights matter.
Many travellers choose Mafia when they want the coast to feel more natural, quiet and marine-focused. It is especially strong after Nyerere or Ruaha, where the safari experience is already remote and less crowded.
Mafia is less convenient than Zanzibar, but that is part of its character. It rewards travellers who are comfortable with smaller-scale lodges, fewer crowds and a slower island rhythm. The main planning decision is whether the extra logistics are worth the quieter experience you gain.